West Lebanon — Nearly three years and $20.3 million in construction costs later, the busiest commercial shopping strip in the Upper Valley appeared to be running smoothly as the final hours of the holiday gift-buying crunch ticked down yesterday.

The infrastructure improvements funded by the New Hampshire Department of Transportation have added new lanes and tweaked traffic signal timing at the Interstate 89 interchange on the Route 12A corridor, along with the freeway underpass connecting Kmart Plaza and the Upper Valley plaza, which opened two months ago — just in time for the other notoriously busy shopping day, Black Friday.

“There are many ways to skin a cat now,” said N.H. DOT project administrator Peter Kehoe of the new underpass connector. “The savvy West Lebanon drivers will get this thing all figured out.”

At least one Upper Valley resident was ready to test the waters yesterday. Robert Mollica, a resident of Randolph for about 20 years, said he planned to use the underpass for the first time, in order to get from the Upper Valley plaza over to the Lebanon Pet and Aquarium Center.

“We’re going to make sure it’s not tolled,” he said with a laugh.

Jokes aside, Mollica said the underpass appeared to make a difference yesterday as he shuttled around five stores to squeeze in last-minute holiday shopping.

“It’s freeing up that mess over there,” he said, as he stood in the Upper Valley plaza parking lot and pointed to the Interchange Drive intersection.

Jim and Susan Metz have lived in Fairlee for about 25 years — long enough, they said, to know that traffic in West Lebanon this year has been relieved by the roadway upgrades long in the making.

“It’s a big improvement,” said Jim Metz, who sported a red Santa hat as he exited Kohl’s with his wife. “That tunnel there connecting the plazas is definitely a help.”

Susan Metz said that they’ve used the tunnel many times since it opened to avoid waiting for the traffic signals along the Route 12A strip, though she wasn’t sure that too many people knew about it yet. Jim Metz laughed as he said that was just fine with him.

“I don’t know if there could be better signage or something, but if you keep it a secret, I’ll still use it,” he said.

It’s not just shoppers who are relieved by the smoother flow of traffic.

Lebanon Police Captain Tim Cohen said that phone calls from residents complaining about traffic on 12A, which reliably pour in around the holidays, have not been ringing in to the station as frequently this year.

“You’re still trying to fit five gallons of water into a one-gallon bucket, it’s always going to be a challenge,” said Cohen. “But we really think the situation has gotten a whole lot better.”

More improvements are yet to come, according to Kehoe, who said that traffic signal timing for the Kmart Plaza intersection for Kmart plaza would be tweaked next month to be completed before the end of February. He added that more and more people will begin to make use of the freeway underpass, which should further alleviate congestion.

Cohen agreed with Kehoe that more people could be taking advantage of the underpass, but he said he too was guilty when it came to not making frequent use of the new roadway.

Just last week, Cohen said, he finished up shopping in the Upper Valley Plaza and got in line for the intersection to turn left toward Kmart.

“It wasn’t until I got onto (Route) 12A and I was like, ‘Darn, what was I thinking?’ ” he said.